Effect of various surface treatment methods on repair bond strength of composite restorations

In some cases repair of composite resin restorations is preferable to replacement. Various surface treatment methods have been introduced to improve the weak bond strength between the new and old composite resins. The aim of this study was to evaluate the effect of various surface treatment methods on repair bond strength of composite resin restorations. In this in vitro study, 56 composite resin specimens (Filtek Supreme) were prepared and randomly divided into seven groups (one control group and six experimental groups). Then one of the surface treatment methods was used in the experimental groups as follows: group 1: diamond bur + phosphoric acid + bonding agent (Single Bond); group 2: diamond bur + phosphoric acid + silane + Single Bond; group 3: air abrasion (50-µm AL2O3 particles) + phosphoric acid + Single Bond; group 4: air abrasion (50-µm AL2O3 particles) + phosphoric acid + Silane + Single Bond; group 5: diamond bur + phosphoric acid + Clearfil Repair; group 6: diamond bur + phosphoric acid + Clearfil SE Bond. After bonding fresh composite resin, all the specimens were stored in distilled water at 37°C for 24h prior to measuring shear bond strength using a universal testing machine. Data were analyzed with one-way ANOVA and Tukey test (α=0.05). The highest bond strength values were recorded in groups 2 and 5, with no significant differences (p value = 0.064); the lowest bond strength was recorded in group 1. Clearfil SB exhibited better results than Single Bond (p value = 0.039) and Clearfil Repair Bond exhibited better results than Clearfil SB Bond (p value = 0.038). Surface treatment with diamond bur was more effective than air abrasion. Use of silane was affective in increasing bond strength. Clearfil Repair Bond had the best effect on repair bond strength of composite resins.